Medical Pump

ABSTRACT

Medical pumps for water jet surgery are known. The invention relates to a pump comprising at least two pistons provided with piston rods for displacing the pistons in cylinders and for coupling to a pump actuation device, a cylinder head for closing the cylinders, and valve means for respectively connecting a pressure chamber in the cylinder to at least one fluid inlet and at least one fluid outlet. Said fluid outlet is connected to the fluid inlet in a communicating manner by means of an adjustable pressure regulating valve, in such a way that the pressure in the fluid outlet can be limited to a predetermined maximum value so that operation of the pump can be.

RELATED U.S. APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO MICROFICHE APPENDIX

Not applicable.

FIELD OF THE INVENTION

The invention relates to a medical pump, in particular for water jetsurgery.

BACKGROUND OF THE INVENTION

Water jet surgery has been used for some time in liver surgery as thisorgan, like no other, has tissue structures of different firmness(parenchyma, blood vessels and bile ducts) and the applied water jetseparates the tissue being cut, yet leaves the blood vessels and bileducts undamaged. Naturally, a precise control of the cutting pressure isrequired for this.

A further problem of water jet surgery is that the cutting medium mustbe totally sterile (e.g. Ringer solution) as the liquid comes intocontact with body tissue in the closest and most intensive way possible.Ordinary problems such as high reliability, simplicity and economicmanufacture must also be considered.

A medical pump for water jet surgery is described in U.S. Pat. No.6,216,573 B1, as well as DE 203 09 616 U1, which is disposable and thusused only once. The pump efficiency as well as its adjustment, however,are unsatisfactory.

BRIEF SUMMARY OF THE INVENTION

The invention provides a medical pump, in particular for water jetsurgery, which despite simple construction and suitability for singleuse facilitates improved cutting performance.

According to the invention a medical pump comprises at least two pistonswith piston rods for displacing the pistons in the cylinders and forcoupling to a pump actuation device, a cylinder head for closing thecylinders in relation to the pistons, valve means for connecting thepressure chamber with at least one fluid outlet and at least one fluidinlet, whereby the fluid outlet interacts with the fluid inlet via anadjustable pressure control valve in such a way that the pressure in thefluid outlet can be limited to a predetermined maximum value.

As the pump is operated with two piston/cylinder units, an improved andsmoothed out pump capacity can be achieved. The construction is simpleso that economic manufacture is possible. The already improved pumpingof the working fluid is further improved by the pressure control valveas it can be smoothed out and at the same time be adjusted to theapplication requirements.

The valve means and/or the pressure control valve comprise an elastic orelastically pressurized valve membrane. This enables very economicmanufacture and high operational safety.

The valve devices can also comprise two spring-loaded ball check valves,which again are simple to produce.

The pressure control valve is preferably constructed as a power drivenvalve in such a way that the maximum value is adjustable by means ofactuating power on a regulator of the pressure control valve. Thisspecial form facilitates coupling of the medical pump to the pumpactuation device in an advantageous manner, where a particular specificspatial positioning of the pump in relation to the pump actuation deviceis not required. Because the pressure adjustment is not proportional tothe travel but proportional to the force, coupling of the pressurecontrol valve to a regulating unit is not position-dependent (whichwould require accurate adjustment of the pump), it is rather theposition independent force with which the regulator activates thepressure control valve which is important.

The pressure control valve is preferably arranged between fluid inletand fluid outlet in such a way, that on exceeding the maximum value,fluid from the fluid outlet can be directed back to the fluid inlet. Inthis way the pressure can be adjusted independently of the quantity ofpumped fluid.

The pistons or pistons rods are preferably connected securely and in asterile way via bellows, cup seal or similar non-slip seals to thecylinders. Germs can thus not be introduced despite sterile workingfluid and sterile transmission pipes, which can be the case with pumpsknown hitherto. This danger is particularly great as due to pistondisplacement in the cylinders their back ends (in relation to thepressure chambers) are subjected to streams of ambient air and thuscylinders can be contaminated therewith in this area.

The valve devices and/or pressure control valve are preferably housed inthe cylinder head. This results in a simpler setup containing fewerparts.

It is preferred that the cylinders are connected independently to thecylinder head. This simplifies manufacture.

The outlet preferably has fittings for irreversible connection to apressure hose. This avoids a faulty installation of the pump and alsonon-permissible re-use of the pump.

The cylinder head preferably comprises holding devices, in particularlugs into which the catches engage, which are attached to the pumpactuation device. No special measures are thus needed for mounting thepump to the pump actuation device.

An accumulator is provided in a preferred embodiment and is connected tothe fluid outlet in such a way that fluid pressure fluctuations at thefluid outlet are smoothed out due to a low pass function. This resultsin a further smoothing of the cutting jet and thus an improvement of theequipment cutting function desired. The accumulators are preferablysituated in the cylinder head or connected therewith which simplifiesthe assembly of the entire arrangement.

Embodiments of the invention will now be described by way of examplewith reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 3 are schematic block diagrams of different embodiments ofthe medical pump arrangements according to the invention.

FIG. 4 is an exploded view of an embodiment of the pump.

FIG. 5 is a side view of the pump shown in FIG. 4.

FIG. 6 is a section along line VI-VI in FIG. 5.

FIGS. 7 and 8 are partial sectional views through the medical pump inthe pressure control valve area in two respective control positions.

FIG. 9 is a perspective view of a cylinder head of the pump.

DETAILED DESCRIPTION OF THE INVENTION

The same reference numbers will be used for the same parts and partswith the same function.

A pump actuation device 10 is intended for the embodiment of theinvention shown in FIG. 1, which encompasses a motor control 15 for thecontrol of two motors 11,11′, which are connected via gearing 12, 12′and clutch devices 13, 13′ to the piston rods 25,25′. One operator B canoperate the motor control 15 with suitable switches (foot switch orfinger switch), so that the motors 11, 11′ displace the piston rods 25,25′ and thus the pistons 22, 22′ in the cylinders 21, 21′ of pump unit20 alternately via the described train, so that the volume of thepressure chambers 16, 16′ of the pump unit 20 is alternately enlargedand reduced.

In order to seal the pressure chambers 16, 16′ and the pistons 22, 22′in relation to the cylinders 21, 21′ seals 23, 23′ are provided at thepistons 22, 22′. Moreover, the piston rods 25, 25′ maintain sterilitywith cup seals 24, 24′, which are firmly fixed to the cylinders 21, 21′on the one hand and to the pistons rods 25, 25′ on the other. In thisway germs from the ambient air, which without these cup seals 24, 24′would settle on the internal walls of the cylinders 21, 21′ and passthrough the seals 23, 23′, can neither mix with the working fluid norfind their way into the same.

Suction valves 26, 26′ as well as pressure valves 27, 27′ are connectedto the pressure chambers 16, 16′. The suction valves 26, 26′ areconnected via a fluid inlet 6 to a reservoir 9 for the working fluid.The pressure valves 27, 27′ are connected to the pressure hose 5 via afluid outlet 7, which leads to an applicator 8. The pump unit 20 forms adisposable part E together with the reservoir 9 including its contents,pressure hose 5 and applicator 8, which is disposed of after eachoperation, so that the entire setup meets the highest sterilityrequirements possible.

A butterfly valve 14 is intended for adjustment of pressure in thissimple embodiment of the invention (which in addition to the motorcontrol 15) facilitates adjustment of the fluid flow by operator B.

The embodiment of the invention shown in FIG. 2 differs from that inFIG. 1 by virtue of the provision of a pressure control valve 35, whichwith the aid of a valve membrane 36 can open and close a connectingchannel between fluid outlet 7 and fluid inlet 6. The membrane 36 isoperated by an actuator 30 via a push rod 34 and a spring 33, as well asa dynamometer 31. The dynamometer 31 supplies a power proportionaloutput signal to a controller 32, via which an operator B can set amaximum pressure. Instead of a separate dynamometer 31 the operatingcurrent of the actuator 30 can also be measured which is also powerproportional.

This arrangement means that the fluid pressure can be accuratelyadjusted at the applicator 8. Moreover, pressure fluctuations resultingfrom piston operation are smoothed out by the control valve 35. Thepressure control valve 35 owing to its construction operates with themembrane pressurised by fluid, in a power-controlled and not atravel-controlled manner. No pressure adjustment error can thereforeoccur even with dimension tolerances during coupling of the pump unit 20to the pump actuation device 10, as it is not the geometric dimensions(travel) which are important, but the power with which the pressurecontrol valve 35 is operated.

The embodiment shown in FIG. 3 differs from the previously shownembodiments by virtue of the provision of an accumulator 40, whichcomprises a cylinder 44 containing a piston 42 sealed by a seal 43,which is pressurized by a spring 41. A chamber situated above the pistonis connected to the fluid outlet, so that with increasing pressure atthe fluid outlet 7 the spring 41 is compressed and with decreasingpressure the spring 41 drives the piston 42. In this way the pressuredirected to the applicator 8 is smoothed out due to its low passfunction. This accumulator 40 is arranged in a cylinder head 29 whichseals the cylinders 21, 21′. It is also possible to combine the variantsshow here. In particular the pressure control valve 35 can be combinedwith the accumulator 40.

FIG. 4 shows a constructive embodiment of the pump device 20 in anexploded view. In this embodiment the pressure and suction valves 26/27comprise balls 19, which are pressed onto the valve seats via springs 18(not visible in the illustration), in an arrangement that is known inprinciple.

The cylinder head 29 has two sections to which the cylinders 21, 21′ arecoupled, whereby the valves sit between the cylinders 21, 21′ and thecylinder head 29.

It can further be seen from FIG. 4, that the piston rods 25, 25′ havecoupling projections 17, 17′ at their distal ends which serve to createmechanical connections with the coupling systems 13, 13′.

The pistons in this embodiment of the invention are formed by theproximal ends of the piston rods 25, 25′ fitted with caps 28, whichsimultaneously hold seals 23, 23′ firmly on the piston rods 25, 25′.

The pressure hose 5 is fastened irreversibly to the cylinder head 29 viaa connecting piece 37, a crimping piece 38 and an internal pipe which isinserted into the pressure hose 5, whereby after assembly of theconnecting piece 37 (in a known way) in the cylinder head 29 by means ofa catch 45, the connecting piece is held irreversibly in the cylinderhead 29.

From FIGS. 5 and 6 details of the layout become clear in particular inrelation to the construction of the suction valve 26, 26′ or thepressure valve 27, 27′ and especially the layout of the valve seats inthe cylinder head 29 on the one hand and the relevant allocatedcylinders 21, 21′ on the other.

FIGS. 7 and 8 show a section through the pressure control valve 35,which shows that the membrane 36 can be pressed by the push rod 34 ontoa valve seat (FIG. 7 shows the open position and FIG. 8 the closed), sothat between fluid outlet 7 and fluid inlet 6, depending on the positionof the membrane 36, a more or less greater “short circuit” of the pumpunit 20 is produced. As the membrane 36 is pressurized by the fluidoutlet 7, a power-controlled valve is present.

FIG. 4 shows further construction related details of the cylinder head29 and the valve devices (suction valve, pressure valve and pressurecontrol valve) contained therein. Moreover, FIG. 9 shows the lugs, whichare coupled via the pump unit 20 to the pump actuation device 10 or theycan be held firmly on the same.

In an embodiment of the invention not shown here not only is thepressure control valve 35 a membrane valve, but also the two pressurevalves 27, 27′ or suction valves 26, 26′ are designed as membrane valvesinstead of the ball valves shown here. This makes the arrangement evenmore economic. Finally, it is also possible to create the pump in such away that not only are all the valves membrane valves but all themembranes are connected in one piece, so that the number of componentsis decreased still further.

LIST OF REFERENCE NUMERALS

-   E Disposable part-   B Operator-   5 Pressure hose-   6 Fluid inlet-   7 Fluid outlet-   8 Applicator-   9 Reservoir-   10 Pump actuation device-   11,11′ Motor-   12,12′ Gearing-   13, 13′ Clutch system-   14 Butterfly valve-   15 Motor control-   16,16′ Pressure chamber-   17,17′ Coupling projection-   18 Spring-   19 Ball-   20 Pump unit-   21, 21′ Cylinder-   22, 22′ Piston-   23, 23′ Seal-   24, 24′ Cup seal-   25, 25′ Piston rod-   26, 26′ Suction valve-   27, 27′ Pressure valve-   28 Cap-   29 Cylinder head-   30 Actuator-   31 Dynamometer-   32 Controller-   33 Spring-   34 Push rod-   35 Pressure control valve-   36 Valve membrane-   37 Connecting piece-   38 Crimp tube-   39 Internal tube-   40 Accumulator-   41 Spring-   42 Piston-   43 Seal-   44 Cylinder-   45 Catch-   46 Lugs

1. Medical pump, comprising a pump actuating device; at least twopistons with pistons rods for displacing the pistons in cylindersdefined by said pump and coupling the pistons to said a pump actuationdevice; a cylinder head sealing the cylinders; valve means thatrespectively connect a pressure chamber in each of the cylinders with afluid inlets and a fluid outlet; and an adjustable pressure controlvalve is provided, in order adapted to limit the fluid pressure in eachfluid outlet to a predetermined maximum value.
 2. Medical pump accordingto claim 1, wherein said pressure control valve is connected to saidfluid inlet and said fluid outlet in such a way that, when the fluidpressure exceeds said predetermined maximum value, fluid from said fluidoutlet is piped back to said fluid inlet.
 3. Medical pump according toclaim 1, wherein at least one of said valve means or said pressurecontrol valve comprises an elastic valve membrane (36).
 4. Medical pumpaccording to claim 1, wherein said valve means comprise spring-loadednon-return ball valves
 5. Medical pump according to claim 1, whereinsaid pressure control valve comprises an actuator and is apower-controlled valve in which said predetermined maximum value isadjustable by a displacement force acting on said actuator.
 6. Medicalpump according to claim 1, wherein said pistons and said piston rods areconnected to the cylinders in a sealed manner which maintains sterility.7. Medical pump according to claim 1, wherein said valve means devicesare fitted at least in part in said the cylinder head.
 8. Medical pumpaccording to claim 1, wherein said cylinders are individually connectedto said cylinder head.
 9. Medical pump according to claim 1, whereinsaid fluid outlet has connecting devices irreversibly connecting it to apressure hose.
 10. Medical pump according claim 1 wherein said cylinderhead has holding means that holding catches, which are attached to saidthe pump actuation device.
 11. Medical pump according to claim 1,comprising an accumulator which is connected to the fluid outlet andwhich smoothes out pressure fluctuations in the fluid at the fluidoutlet by means of a low pass function.
 12. Medical pump according toclaim 11, wherein said accumulator is located in or is connected to saidcylinder head.
 13. Medical pump according to claim 1, wherein saidpressure control valve is fitted at least in part in said cylinder head.